There is a "science" behind shelf placement decisions and it has to do with height, location on the aisle, colors, lights, and of course the "fee" that the outlet asks for the premium spots. Someone who just fills shelfs (I've done that for a toystore a few decades ago, for a a couple of months).

Depends whether someone gets to just fill the shelf as per plan or has the curiosity to ask "WHY", noticing why X things fly off the shelf why Y things two shelves lower stay there forever. This curiosity builds the critical thinking 'muscle' and can motivate a shelf-filler to switch into marketing (hypothetical scenario has to do with a 17yo working part time and then deciding to studio marketing)(I didn't study marketing) :)